Thermoplastic polyolefin (TPO) formulations from polypropylene/propylene-based elastomer blends are commonly used in TPO for the extrusion of roofing and waterproofing membranes. In general, they are filled with 30 to 45 wt % of halogen-free flame retardants like aluminum trihydrate (ATH) or magnesium hydroxide [Mg(OH)2], and have a flexural modulus in the range of 80 to 100 MPa. They pass standard fire resistance requirements as e.g. Euroclass D and E according to EN 119256-2, as well as ASTM- and EN-system tests, e.g. ENV 1187 t1 to t4. TPO formulations are in use for thicker membranes like single-ply roofing when installed on substrates, or when reduced fire resistance requirements are applicable. Until now, Euroclass A2 fire-resistance levels according to EN 11925-2, or similar demanding and vertical fire tests could not be matched with halogen-free olefin formulations. Table 1 gives an overview of the European fire standards.
TABLE 1European Fire Standards and Classes and for Infrastructure MembranesSystem TestsEuro-Laboratory TestsGermanyclassSmall burnerSBI (EN 13823)OtherDIN 4102UKFranceNordicA1EN 1182Non-Non-Non-EN 1716combustiblecombustiblecombustibleA2Figra0.2 MJ =< 120EN 1182A2Non-M0/M1WsEN 1716combustibleTHR600 s =< 7.5 MJBEN 11925-2Figra0.2 MJ =< 120BS 7837B1BS 476 part 6M1Class 1(30 s/30 s)Wsand 7THR600 s =< 7.5 MJB-S1-d0CEN 11925-2Figra0.4 MJ =< 250B1Class 1M2Class 2(30 s/30 s)WsTHR600 s=< 15 MJDEN 11925-2Figra0.4 MJ =< 750B2Class 3 ENVM3/M4Class 3(30 s/30 s)WsENV 1187 t11187 t4ENV 1187 t3ENV 1187 t2EEN 11925-2B2M4not allowed(15 s/20 s)ENV 1187 t1FB3
Coated fabrics for applications like architectural textiles, banners, tarpaulins or artificial leather may require higher loadings of flame retardants to pass stringent test requirements like EN 11925-2 (small burner test) according to Euroclass B or BS 7837. EN 13823 (single burning item test) is required to be passed in a classification of B-S1-dO.
Flexible, coated fabrics for applications demanding fire resistance at the level of Euroclass B are commonly made from polymers with intrinsic fire resistance like polyvinylchloride, polyurethanes, fluoroelastomers or silicones.
At the same time, compounds for such applications have to show processability in extrusion coating, and good fabric penetration and adhesion. In the final application, they usually have to fulfill various properties like flexibility (a common target is a flexibility modulus below <30 MPa), weldability, abrasion resistance, mechanical strength, printability, weathering- and UV-resistance, and fire resistance. To fulfill these demanding combinations of requirements, polyvinylchloride, fluoropolymers, or even silicones, are in common use today. TPOs were not used as they could not comply with the demanding property requirements. In particular, they lack flexibility in combination with sufficient fire resistance.
WO 2005/090427 describes a multi-block copolymer comprising in polymerized form ethylene and one or more copolymerizable comonomers, said copolymer containing therein two or more segments or blocks differing in comonomer content, crystallinity, density, melting point or glass transition temperature.
WO 2006/101924 describes blends of at least two polyolefins with ethylene/α-olefin (multi-block) interpolymers with improved compatibility.
WO 2006/101932 describes compositions comprising ethylene/α-olefin (multi-block) interpolymers and fillers.
WO/2011/008336 describes a multilayer structure comprising a top skin layer comprising a propylene/alpha-olefin copolymer blended with at least one other component; a middle foam layer comprising a propylene/alpha-olefin copolymer; and a bottom fabric layer comprising a nonwoven, polymeric, spunbond material.